Apex domains cannot have CNAME records.
Question and response
Question
dig medallia.com.au. NS
Answer
medallia.com.au. 5 NS ns-684.awsdns-21.net.
medallia.com.au. 5 NS ns-1398.awsdns-46.org.
medallia.com.au. 5 NS ns-1925.awsdns-48.co.uk.
medallia.com.au. 5 NS ns-44.awsdns-05.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0